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In the electric heating industry, some companies assert that their products are more economical to run than those of competitors. But can you trust these claims?
The short answer is NO!
All electric radiators and electric heaters have the same efficiency. The efficiency of converting electricity into heat by using a resistance element is 100%. It cannot be any greater than 100% or any less. This is determined by Joule’s law in physics.
Can the materials used in the construction make any difference to this efficiency?
NO. The heat is produced by the heating element, the other materials i.e. Steel or Aluminium for the body and oil, water, ceramic, fireclay, soapstone etc for the internals cannot produce any extra heat. They can only transfer the heat produced by the heating element to the room.
Is it true that Aluminium has better conductivity than steel?
Yes this is true, but what does it mean?
With electric radiators, it just means that the initial heat up time of the Aluminium heater will be a little faster although if using other dense materials inside like soapstone it will still be quite slow.
What about the Soapstone or other materials used inside the heater? Can they reduce the energy use?
No. These materials can only transfer the heat produced by the heating element to the radiant surface of the heater. If they stay warm for a while when switched off, this is not extra heat or free heat, it is just heat that you have paid for that is not yet in the room. A radiator should be designed to disperse heat into the room quickly in order to warm your room.
How does room heat loss affect the amount of time a radiator will be on for?
This is all about the radiator output in watts vs the room heat loss in watts
If a room has a heat loss of 500 watts per hour through the windows, walls etc and we use a 500 watt heater in the room it will be on all the time. If we use a 1000 watt heater in this room it will be on 50% of the time. A 2000 watt would be on 25% of the time.
This is true of any electric heater or radiator that has a thermostat. In practice all electric radiators have good thermostats and timing systems due to the ERP Lot20 regulations that came in to power 2018.
What about heat loss through the back of the radiator?
This is only applicable when the radiator is mounted on an outside wall. The amount of heat loss will depend on the wall construction, the wall insulation and the outside temperature. If the wall is very well insulated, the heat loss will be very small. If you need to mount the radiators on outside walls, you can use RADFLEK at the back of the radiator which is proven to reduce heat loss by 45%. This will cost around £5 per heater and is very easily fitted.
If the radiator is mounted on an internal wall, there will not be any heat loss as the room temperatures will be the same as each other in internal rooms.
A High Heat Retention storage heater will not lose any heat through the back of the heater as the core is completely insulated at the back, front, top, bottom and both sides.
What is the difference between an oil filled electric radiator and a ceramic, fireclay or soapstone filled electric radiator?
The oil filled heater will heat up a bit faster and also cool a little quicker. The ceramic, fireclay or soapstone will heat up slower and cool slower. With both you get the same heat for the same money.
There are some companies claiming to have independent tests showing lower running costs, what about that?
We’ve seen tests that are claimed to be from Huddersfield University when actually they are in house tests conducted by the company (we have verification of this)
We’ve also seen tests conducted by BSRIA and BRE which just show the accuracy of the thermostat and how well the heater maintained a set temperature.
Some of these tests have been used to claim reduced running costs. For example one test shows a radiator with 1600 watts power tested in a room with 600 watts heat loss. It was on for 38% of the time because 600 is 38% of 1600. It is claimed by the manufacturer that this heater is only ever on for 38% of the time but this would only be true in this environment. If we put the 1600 watt heater in a room with 800 watts heat loss for example, it would be on 50% of the time or with 1600 watts heat loss it would be on 100% of the time.
Some use terms like ‘38% ratio of consumption’. This is meaningless, it all depends on the room heat loss.
The UK government SAP and EPC states that all electric heaters and electric radiators have the same efficiency and running costs.
The lowest running cost electric heating ( apart from heat pumps ) according to the UK government SAP and EPC are High Heat Retention storage heaters which officially have 40% lower running costs than any electric radiator. This is due to efficient use of the cheaper overnight electricity rates.
In summary, are you saying that all electric heaters have the same energy use and running costs as each other?
Yes, exactly. The only way to reduce running costs is to use a cheap rate tariff over night to store heat at the cheaper rate. The best product to choose for lower running costs is a High Heat Retention storage heater.
To be a true High Heat Retention storage heater it must be government tested and listed on the government database of approved heaters here: https://www.ncm-pcdb.org.uk/sap/pcdbsearch.jsp?type=391&pid=44
Can you trust electric heating companies?
Some can be trusted to tell the truth and some can’t. Hopefully the information above will help you decide where to place your trust when deciding which electric heating product to purchase.